The Thought-Men of Mercury by Russ Winterbotham

It was neither night nor day, but a sort of nether world of twilight. The huge fern-like plants, flashing phosphorescence under the green corona light, seemed to close in after Cappy Upjohn and Terry Hall like prison bars in the windows of a dungeon.

Cappy, who was leading the way, paused and waited for Terry. As the huge, leonine man turned, his lips curled into a taunting smile.

Terry's eyes moved from side to side, watching the weird shadows, dodging the sweep of the giant ferns as they moved in the wind.

"Scared!" Cappy ridiculed.

"I can't help it!" the younger man said. "This place gives me the creeps."

Cappy's great laugh echoed above the howl of the winds. "This is Mercury. Half day, half night everlastingly. Right here is the battleground of roasting heat and perpetual cold. A twenty-mile strip of habitable land between two kinds of hell. What the devil did you expect, Tenderfoot?"

Cappy grunted in disgust, turned and picked his way through the ferns. Terry, his jaw set grimly, followed. Cappy had been through all this before. Twice he'd landed on Venus, and he'd been with the only previous expedition to Mercury. But Terry knew that fear was a human emotion, and that there were things even Cappy was afraid of.

The wind died a moment. Between an opening in the ferns Terry caught a glimpse of a ghostly face, more simian than an ape's, less human than a man's. At the same time he felt something that was like a breeze through his brain. A painless stab of thought,

"Cappy—look!" Terry pointed at the face peering through the opening in the ferns, and his hand clawed at the rifle he had slung over his shoulder. In all respects it was like an old-fashioned gun, but it fired a deadly bullet that was capable of complete annihilation of whatever it hit. A single bullet from a flourobeam gun was powerful enough to wipe out a steel ball ten feet in diameter.

But Terry's hands slipped away from his gun. He recognized his action as more than fear. It was panic.